Produção de biomassa do urucum (Bixa orellana L.) e estoque de serrapilheira em um SAF no Agreste potiguar

Abstract

Agroforestry systems that combine productive species with fertilizer plants for biomass production and use as soil cover stand out as promising agricultural models in the face of existing socio-environmental challenges. Given the scarcity of studies on these fertilizer species, the aim of this study was to quantify the aerial biomass production of achiote (Bixa orellana L.) and the stock of litter present in an AFS (agroforestry system) in Agreste Potiguar. In 2019, the system was implemented under two treatments, in areas I and II with and without fertilization and mulching, respectively. After 4 years, the aerial biomass production of achiote was determined by weighing the biomass from two prunings, at an interval of 3 months, in the middle of the dry season and the beginning of the rainy season. For both collections, ten randomly selected achiote trees per area were pruned and weighed. Then 300 g samples were taken from the leaves, branches and stems, which were dried in an oven until they were constant weight. As for the litter, samples from both areas were collected using a 30 x 30 cm² metal frame. From the 4 rows in each area, 2 were selected for the collection of 20 samples, dropping the frame at 5 central points per row between the fruit trees. The material was then separated into the following fractions: branches and leaves and miscellany, and the dry mass was obtained in a process similar to that for biomass. Afterwards, the total number of species present in the AFS was inventoried by measuring the circumference at breast height (CBH) with a tape measure, and the total height was determined using a graduated ruler. Achiote has potential as a fertilizer plant for AFSs in the Agreste Potiguar region, with biomass production from pruning ranging from 0.42 t.ha-¹ to 2.44 t.ha-¹. The litter stock of achiote in the AFS was, on average, 35 t.ha-¹, indicating that it accumulates enough litter to keep the soil covered in the tree rows.